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As the most abundant gas in Earth’s atmosphere, nitrogen has been an attractive option as a source of renewable energy. But nitrogen gas—which consists of two nitrogen atoms held together by a strong, triple covalent bond—doesn’t break apart under normal conditions, presenting a challenge to scientists who want to transfer the chemical energy of the bond into electricity.
Now, researchers in China have developed a rechargeable lithium-nitrogen (Li-N–) battery with the proposed reversible reaction of 6Li + N– ⇋ 2Li–N. The assembled N– fixation battery system, consisting of a Li anode, ether-based electrolyte, and a carbon cloth cathode, shows a promising electrochemical faradic efficiency (59%).
The “proof-of-concept” design, described in an open-access paper in the journal Chem, works by reversing the chemical reaction that powers existing lithium-nitrogen batteries. Instead of generating energy from the breakdown of lithium nitride (2Li N) into lithium and nitrogen gas, the researchers’ battery prototype runs on atmospheric nitrogen in ambient conditions and reacts with lithium to form lithium nitride. Its energy output is brief but comparable to that of other lithium-metal batteries.
Although it constitutes about 78% of Earth’s atmosphere, N in its molecular form is unusable in most organisms because of its strong nonpolar N≡N covalent triple-bond energy, negative electron affinity, high ionization energy, and so on. In terms of energy efficiency, the honorable Haber-Bosch process, which was put forward more than 100 years ago, is the most efficient process for producing the needed N fertilizers from atmospheric N in industrial processes. However, the energy-intensive Haber-Bosch process is inevitably associated with major environmental concerns under high temperature and pressure, leaving almost no room for further improvement by industry optimization.
… Inspired by rechargeable metal-gas batteries such as Li-O , Li-CO , Li-SO , Al-CO , and Na-CO (which have attracted much attention because of their high specific energy density and ability to reduce gas constituent), research on Li-N batteries has not seen any major breakthroughs yet. Although Li-N batteries have never been demonstrated in rechargeable conditions, the chemical process is similar to that of the previously mentioned Li-gas systems. During discharging reactions, the injected N molecules accept electrons from the cathode surface, and the activated N molecules subsequently combine with Li ions to form Li-containing solid discharge products. From the results of theoretical calculations, the proposed Li-N batteries show an energy density of 1,248 Wh kg , which is comparable to that of rechargeable Li-SO and Li-CO batteries.
The research team demonstrated that a rechargeable Li-N battery is possible under room temperature and atmospheric pressure with the following reversible battery reactions:
The team investigated the use of Ru-CC and ZrO2-CC composite cathodes to improved the N fixation efficiency. Li-N2 batteries with catalyst cathodes showed higher fixation efficiency than pristine CC cathodes.
This promising research on a nitrogen fixation battery system not only provides fundamental and technological progress in the energy storage system but also creates an advanced N /Li N (nitrogen gas/lithium nitride) cycle for a reversible nitrogen fixation process. The work is still at the initial stage. More intensive efforts should be devoted to developing the battery systems. —senior author Xin-Bo Zhang, of the Changchun Institute of Applied Chemistry, part of the Chinese Academy of Sciences
This work was financially supported by the Ministry of Science and Technology of China and the National Natural Science Foundation of China.

As the most abundant gas in Earth's atmosphere, nitrogen has been an attractive option as a source of renewable energy. But nitrogen gas -- which consists of two nitrogen atoms held together by a strong, triple covalent bond -- doesn't break apart under normal conditions, presenting a challenge to scientists who want to transfer the chemical energy of the bond into electricity. In the journal Chem on April 13, researchers in China present one approach to capturing atmospheric nitrogen that can be used in a battery.
The "proof-of-concept" design works by reversing the chemical reaction that powers existing lithium-nitrogen batteries. Instead of generating energy from the breakdown of lithium nitride (2Li3N) into lithium and nitrogen gas, the researchers' battery prototype runs on atmospheric nitrogen in ambient conditions and reacts with lithium to form lithium nitride. Its energy output is brief but comparable to that of other lithium-metal batteries.
"This promising research on a nitrogen fixation battery system not only provides fundamental and technological progress in the energy storage system but also creates an advanced N2/Li3N (nitrogen gas/lithium nitride) cycle for a reversible nitrogen fixation process," says senior author Xin-Bo Zhang, of the Changchun Institute of Applied Chemistry, part of the Chinese Academy of Sciences. "The work is still at the initial stage. More intensive efforts should be devoted to developing the battery systems."
This work is financially supported by the Ministry of Science and Technology of China and the National Natural Science Foundation of China.
Chem, Ma and Bao et al.: "Reversible Nitrogen Fixation Based on Rechargeable Lithium-Nitrogen Battery for Energy Storage" http://www.cell.com/chem/fulltext/S2451-9294(17)30129-8
Chem (@Chem_CP) is the first physical science journal published by Cell Press. The sister journal to Cell, Chem provides a home for seminal and insightful research and showcases how fundamental studies in chemistry and its sub-disciplines may help in finding potential solutions to the global challenges of tomorrow. Visit http://www. . To receive Cell Press media alerts, contact press@cell.com.

A new small-molecule strategy could help target cancer drugs selectively to tumors with the help of click chemistry (Nat. Chem. Biol. 2017, DOI: 10.1038/nchembio.2297).
Many cancer drugs attack healthy tissue in addition to tumors, leading to harmful side effects. So scientists want to target therapeutics to cancer cells more selectively.
One such approach that has reached the clinic is antibody-drug conjugates. Antibodies recognize antigens, such as HER2 on some breast cancer cells, allowing antibody-attached drugs to kill those cancer cells selectively. But disease-specific antigens aren’t always available, and antibody-drug conjugates are costly and must be administered intravenously.
A group led by Jianjun Cheng of the University of Illinois, Urbana-Champaign (UIUC), Lichen Yin of Soochow University, and Xuesi Chen of Changchun Institute of Applied Chemistry has now come up with a strategy called active tissue targeting via anchored click chemistry (ATTACK) that they’ve tested in mice and that may have advantages over antibody-drug conjugates.
In the two-step ATTACK process, the researchers first give tumor-bearing mice an ether-protected sugar that carries an azide group. Cells can deprotect and then metabolize the sugar, which then gets attached to glycoproteins in the cell membrane. Because cancer cells proliferate quickly, they overexpress some enzymes, two of which catalyze deprotection of the azido sugar. This makes cancer cells more likely than normal cells to be tagged by the bioorthogonal azide groups.
In the second step, researchers give the mice an anticancer drug conjugated to dibenzocyclooctyne (DBCO). DBCO’s alkyne group undergoes a selective click-chemistry reaction with azides, thus recruiting the conjugated drug selectively to azide-decorated cancer cells.
In the mice, ATTACK improved drug-targeting selectivity 50% for treated tumors over untreated ones. And a DBCO-doxorubicin conjugate was significantly more effective and much less toxic than doxorubicin alone at treating colon cancer and two forms of breast cancer in mice—improvements the researchers plan to quantify in future work.
ATTACK has potential advantages over antibody-drug conjugates: It doesn’t require that a given cancer have a cell-surface antigen because the method creates its own targets; and ATTACK’s small-molecule agents could be orally available and less expensive to make.
The strategy “is very elegant” for achieving selective action because the ether is deprotected primarily in cancer cells, comments targeted drug delivery expert Liangfang Zhang of the University of California, San Diego. “It’s great work that will generate a lot of interest in the field.”
“The approach is clever in that it translates an intracellular molecular signature, cancer-related enzyme expression, to a cell-surface signature, azide groups that allow for targeting,” says bioorthogonal chemistry specialist Carolyn R. Bertozzi of Stanford University, adding that she is interested to see if the approach can be developed commercially.

An international research team has prepared a set of lanthanide antimony clusters that represent the first isolable compounds containing an all-metal antiaromatic ring. The achievement continues to expand the concept of aromaticity beyond its humble beginnings 150 years ago.
Researchers including Xue Min and Zhong-Ming Sun of Changchun Institute of Applied Chemistry and Ivan A. Popov and Alexander I. Boldyrev of Utah State University created a series of anions, [Ln(Sb ) ]3–, where Ln is La, Y, Ho, Er, or Lu. They made the anions by treating lanthanide benzyl complexes with the Zintl cluster complex K Sb in pyridine solvent and then isolating the anions as potassium cryptand salts.
On the basis of X-ray crystal structures and computational bonding analysis, the team says the rhombic Sb rings that serve as ligands to the lanthanide metals are antiaromatic (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201600706).
The concept of antiaromaticity has a storied history. In 1865, German chemist August Kekulé proposed the concept of aromaticity to explain the unusual properties of benzene, a planar carbon ring that exhibits high stability and low reactivity. In 1931, German chemist Erich Hückel added to the definition that aromatic compounds have a delocalized 4n﻿﻿﻿ + 2 π-electron system. In 1965, on the centennial of Kekulé’s proposal, Columbia University’s Ronald Breslow proposed the idea of antiaromaticity—the antonym of aromaticity—to characterize planar carbon rings with a 4n π-electron system that exhibit low stability and high reactivity.
Aromaticity and antiaromaticity were originally thought to be purely the domain of organic chemistry. But during the past 20 years, chemists have shown that this organic boundary is flexible. In 1995, Gregory H. Robinson and coworkers of the University of Georgia isolated the sodium salt of a phenyl-substituted Ga ring with two π﻿ electrons, introducing the concept of metalloaromaticity.
In 2003, Boldyrev’s group in collaboration with Lai-Sheng Wang, now at Brown University, followed suit by reporting Li Al –, which includes an antiaromatic Al 4– ring containing four π electrons. However, the gaseous molecule was created in a laser-based experiment and couldn’t be trapped in a condensed state.
With the [Ln(Sb ) ]3– series, chemists now have the first examples of isolable inorganic antiaromatic compounds. As a key feature, each Sb ring stabilized by the lanthanide metal has four delocalized π electrons. The Sb unit is analogous to cyclobutadiene, Boldyrev says, which is the quintessential antiaromatic organic compound.
“Antiaromaticity in these all-metal systems is very nice,” Breslow tells C&EN. “It is gratifying to see that our proposal, which was quite unexpected when we first made it for organic systems, has such generality.”
Further advances of aromaticity and antiaromaticity into metal territory will be valuable for understanding the properties of metal clusters, bulk metals, and alloys, Boldyrev and Sun add, which could be handy for making thin-film electronic materials.
“From a conceptual perspective, this is another example of the concept of aromaticity—in this case antiaromaticity or antimetalloaromaticity—being extended beyond the realm of carbon,” Robinson says. “More important, taking all of this work into consideration, aromaticity and metalloaromaticity seem to be foundational principles throughout the whole of chemistry.” This article has been translated into Spanish by Divulgame.org and can be found here.

Photodetectors, which are used in a wide range of systems and devices--from smartphones to space stations--are typically only sensitive to light within a certain narrow bandwidth, which causes numerous problems to product developers. Together with their colleagues from China and Saudi Arabia, scientists at MIPT have found a way to address this. According to their study, published in Advanced Functional Materials, treating an ordinary photodetector with UV light can turn it into a high bandwidth device.
"There is a lot of demand for photodetectors that are sensitive to a wide range of frequencies, but they are difficult to design. It's hard to find the right materials, because the substances that permit ultraviolet light tend to be nontransparent to infrared radiation, and vice versa. We found a way to 'broaden' the spectral response of photodetectors," says Vadim Agafonov, head of the Molecular Electronics Center at MIPT, a coauthor of the paper.
The research team that also includes his colleagues from the Changchun Institute of Applied Chemistry (China) and King Saud University (Saudi Arabia) studied polymer photodetectors based on the internal photoelectric effect, i.e., the redistribution of electrons within a polymer under the influence of light, resulting in electrical conductivity. Photodetectors based on organic materials have a number of advantages over their conventional inorganic counterparts, including their low cost, easier manufacturing, and physical flexibility. It turned out that by interacting with the surfaces of certain elements of the device, UV radiation can alter its sensitivity.
The researchers conducted an experiment whereby a polymer-based photodetector incorporating zinc oxide (ZnO) nanoparticles was exposed to UV light for 30 seconds. As a result of this, they achieved a high-performance photodetector with a much broader spectral response and a maximum external quantum efficiency (EQE) of 140,000%, as compared to the 30% measured before UV treatment. The EQE of a photodetector is an important figure of merit defined as the ratio between the number of "dislodged" electrons and the number of incident photons. To put that in perspective, whereas before irradiation 10 photons generated just three electrons, after UV treatment the same number of photons produced 14,000 photoelectrons. However, the amount of noise experienced by the device was also greater due to an increased dark current, which is generated in the detector even when no photons are entering the device.
The researchers attribute the dramatic effect of UV light on detectors to the detachment of oxygen atoms from the zinc oxide molecules. During the manufacturing of a photodetector, oxygen molecules are adsorbed onto the surface of the semiconductor particles, whereby oxygen captures electrons from the conduction band. As a result, the captured electrons can no longer act as charge carriers. This means that the zinc oxide layer becomes a barrier that affects electron transport.
UV light treatment causes some of the valence electrons to migrate into the conduction band, driven by the radiation absorbed by the ZnO particles. The freed up electrons can then act as charge carriers, generating photocurrent even at the minimal measurable optical power intensity of 60 pW?×?cm?² (picowatts per cm²) under the bias voltage of ?0.5 V.
"You can thus convert a polymer-based photodetector into a highly sensitive broadband device. The process itself is quick, cheap, and efficient, which is important for practical applications," says Vadim Agafonov.
According to the paper, it is sufficient to treat a photodetector with UV light once during its manufacturing in order to achieve the broad spectral response. Moreover, the newly acquired properties of the device will remain unchanged after the manufacturing process is over, as the semiconductor layer will be sealed by a layer of aluminum protecting it from oxygen.
The researchers hope to eliminate the "side effects" that arise after irradiating the detector with UV light (e.g., a sharp increase in dark current), without sacrificing the high performance and wide spectral range of the device. Photodetectors that have been treated in the proposed way could be used anywhere from imaging to atmospheric sensing.

Photodetectors, which are used in a wide range of systems and devices — from smartphones to space stations — are typically only sensitive to light within a certain narrow bandwidth, which causes numerous problems to product developers. Together with their colleagues from China and Saudi Arabia, scientists at Moscow Institute of Physics and Technology (MIPT) have found a way to address this. According to their study, published in Advanced Functional Materials ("Ultrahigh Gain Polymer Photodetectors with Spectral Response from UV to Near-Infrared Using ZnO Nanoparticles as Anode Interfacial Layer"), treating an ordinary photodetector with UV light can turn it into a high bandwidth device.
“There is a lot of demand for photodetectors that are sensitive to a wide range of frequencies, but they are difficult to design. It’s hard to find the right materials, because the substances that permit ultraviolet light tend to be nontransparent to infrared radiation, and vice versa. We found a way to ‘broaden’ the spectral response of photodetectors,” says Vadim Agafonov, head of the Molecular Electronics Center at MIPT, a coauthor of the paper.
The research team that also includes his colleagues from the Changchun Institute of Applied Chemistry and King Saud University studied polymer photodetectors based on the internal photoelectric effect, i.e., the redistribution of electrons within a polymer under the influence of light, resulting in electrical conductivity. Photodetectors based on organic materials have a number of advantages over their conventional inorganic counterparts, including their low cost, easier manufacturing, and physical flexibility. It turned out that by interacting with the surfaces of certain elements of the device, UV radiation can alter its sensitivity.
The researchers conducted an experiment whereby a polymer-based photodetector incorporating zinc oxide (ZnO) nanoparticles was exposed to UV light for 30 seconds. As a result of this, they achieved a high-performance photodetector with a much broader spectral response and a maximum external quantum efficiency (EQE) of 140,000 percent, as compared to the 30 percent measured before UV treatment. The EQE of a photodetector is an important figure of merit defined as the ratio between the number of “dislodged” electrons and the number of incident photons.
To put that in perspective, whereas before irradiation 10 photons generated just three electrons, after UV treatment the same number of photons produced 14,000 photoelectrons. However, the amount of noise experienced by the device was also greater due to an increased dark current, which is generated in the detector even when no photons are entering the device.
The researchers attribute the dramatic effect of UV light on detectors to the detachment of oxygen atoms from the zinc oxide molecules. During the manufacturing of a photodetector, oxygen molecules are adsorbed onto the surface of the semiconductor particles, whereby oxygen captures electrons from the conduction band. As a result, the captured electrons can no longer act as charge carriers. This means that the zinc oxide layer becomes a barrier that affects electron transport.
UV light treatment causes some of the valence electrons to migrate into the conduction band, driven by the radiation absorbed by the ZnO particles. The freed up electrons can then act as charge carriers, generating photocurrent even at the minimal measurable optical power intensity of 60 pW x cmv-2 (picowatts per cm2) under the bias voltage of -0.5 V.
“You can thus convert a polymer-based photodetector into a highly sensitive broadband device. The process itself is quick, cheap, and efficient, which is important for practical applications,” says Agafonov.
According to the paper, it is sufficient to treat a photodetector with UV light once during its manufacturing in order to achieve the broad spectral response. Moreover, the newly acquired properties of the device will remain unchanged after the manufacturing process is over, as the semiconductor layer will be sealed by a layer of aluminum protecting it from oxygen.
The researchers hope to eliminate the “side effects” that arise after irradiating the detector with UV light (e.g., a sharp increase in dark current), without sacrificing the high performance and wide spectral range of the device. Photodetectors that have been treated in the proposed way could be used anywhere from imaging to atmospheric sensing.

Chinese scientists have developed a flexible lithium-based battery that is based on Chinese brush painting. More
Scientists in China have developed a flexible, rollable, foldable battery inspired by traditional Chinese calligraphy involving ink on paper.
Worldwide demand for flexible electronics is rapidly growing, because the technology could enable such things as video screens and solar panels to bend, roll and fold. These flexible electronics require batteries that are equally flexible to power them, but conventional batteries are too rigid and bulky to be used in flexible electronics.
Chinese scientists, however, have developed a flexible lithium-based battery that is based on Chinese brush painting. [5 Crazy Technologies That Are Revolutionizing Biotech]
Lithium-ion batteries power most portable devices, from smartphones to tablet computers to laptops. However, so-called lithium-air batteries could, in principle, hold five to 10 times as much energy as a lithium-ion battery of the same weight. This means that lithium-air batteries could theoretically give electric cars the same range as gasoline ones.
Batteries usually contain two electrodes — the anode and the cathode. In a lithium-air battery, the anode is generally made of lithium metal, while the cathode is typically a porous carbon material that allows the surrounding air into the battery. As the lithium reacts with oxygen in the air, it discharges electricity. Recharging the device reverses the process.
The scientists noted that the main component of black painting ink is carbon, and that paper is porous, thin, flexible, light and cheap. They reasoned that ink drawn on paper could serve as a cathode for a lithium-air battery in a very simple manner.
"Due to the ultra-high theoretical energy density of lithium-oxygen batteries, they may be one of the most suitable candidates in the future for the development of flexible electronics," study senior author Xinbo Zhang, a materials scientist at the Changchun Institute of Applied Chemistry in China, told Live Science.
The researchers constructed a battery from a sandwich of three layers — an ink-paper cathode, a sheet of lithium foil as the anode, and a sheet made of glass fibers between the anode and the cathode that permits electrically charged ions to flow between the cathode and anode.
Zhang and his colleagues found their prototype batteries possessed energy-storage capacities comparable to commercial lithium-ion batteries, even after 1,000 cycles of flexing back and forth. They could also easily fold these sheets into battery packs.
In the future, Zhang said he and his colleagues will explore lightweight flexible coatings for these batteries to protect them from corrosion.
Zhang and his colleagues detailed their findings in the Dec. 22 issue of the journal Advanced Materials.
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Ink on paper can act as an electrode in a thin, flexible battery.
Inspired by Chinese brush painting, a team led by Xin-Bo Zhang at the Chinese Academy of Sciences' Changchun Institute of Applied Chemistry fabricated a flexible lithium-air battery using lithium foil and paper with a carbon-based ink (pictured). Electrons are stripped from the foil, creating lithium ions that flow to the inked paper electrode, where they combine with oxygen from the air. The resulting battery can hold a charge even after it has been bent 1,000 times. A foldable pack of four batteries, which weighs less than 2 grams, can supply current for 100 hours.
The technique paves the way for cheap and easily manufactured flexible batteries, the authors say.